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Plague in Rats.
In all treatises dealing with plague, which have been published during the past year or so, one finds a considerable amount of attention devoted to the question of the occurrence of plague infection in rats, and the dangers attached to the presence of such infected vermin in the direct vicinity of man.
Sanitary bodies, although thoroughly convinced as to the presence of such epizootics in certain plague endemic areas, are by no means convinced as to the exact role played by such plague infected animals in epidemiology. In short, much evidence is wanting to prove conclusively, that some relation exists het- ween rat plague and an epidemic of plague.
We may find both present. The epizootic and the epidemic may run concur- rently; yet one finds it difficult to become reconciled to the conclusion that plague is primarily a disease among rats, and that such infected vermin are responsible for the outbreak of the disease amongst the human species.
The present research is an attempt to grasp as thoroughly as possible the whole question of the epizootic. The reader of this report is left to gather his own conclusions from the matter now presented.
Plague in rats is by no means a recent discovery. High rat mortalities were noted by the ancients during epidemics of plague. Classical, medieval aud modern literature furnishes us with many interesting details in regard to the sus- septibility of various animals, especially house vermin, to plague infection. The general lay opinion in regard to the matter is that, during plague epidemics, an increased mortality is observed amongst the animals in the infected district, and that such a death rate is noticeable especially amongst rats.
It would be difficult to determine who propounded the rat theory of plague epidemics. The prominence to the epizootic, during recent years, has arisen out of better acquaintance with the bacteriological and epidemiological aspects of the disease.
AVICENNA in the year 1000, noted the presence of a high rat mortality during plague epidemics. He says:"Et de eis quae significant illud est ut videas Mures et animalia quae habitant, sub terra fugere ad superficiem terrae et parti sedar e.g., commoveri hinc inde sicut animalia ebria.'
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Again NICEPHORUS GREGORAS in 1348 and ORRAEUS in 1771 in their treatises on Medicine, look suspiciously upon rats as having some relation to outbreaks of epidemic plague. Reports such as these are extremely interesting to investigators of the present day, who are endeavouring as far as possible to bring this rodent into close relationship with the occurrence of plague amongst human teings.
Plague research is, at present, directed to the rat, the occurrence of the disease in his body, and the channels through which the plague bacillus is transported from his body to that of man.
SIMPSON, in his Report on Plague in China and Hongkong, has given us an excellent resumé. of the beliefs held by the Chinese in regard to the prevalence of the disease in animals such as rats. It is evident that the opinion is widely diffused amongst the Chinese that there exists some relation between the epizootic and the epidemic.
In their writings the Chinese make frequent mention that during, or imme- diately preceding, plague epidemics, severe epidemics occur amongst their cattle- frequently called Rinderpest-their fowls, and their house vermin.
In dealing with the subject of Rat Plague, I have endeavoured to more or less systematise the subject. The latter is a large one, and unless some method be employed in order to grasp the subject as widely as possible, points of great importance are bound to be overlooked.
1. General Remarks.
Rat Plague.
2. Symptoms of Acute Rat Plague.
3. Post-appearances of Acute Rat Plague. 4. Symptoms of Chronic Rat Plague.